The primary purpose of the proposed research is to capitalize on an initial investment of the National Institute on Aging (AGO4563) which in 1984 launched the only longitudinal behavioral genetic analysis of individual differences in functioning later in life. The study, called the Swedish Adoption/Twin Study of Aging (SATSA), uses the powerful design of twins reared together and twins read apart, and has become a landmark study of gerontological genetics. SATSA now has the opportunity to study this unique sample a decade later through the inclusion of a third wave of in-person testing (IPT3) and a fourth wave of questionnaire assessment (Q4). Approximately 600 individuals will be tested in IPT3, and 2,000 individuals will receive Q4. Longitudinal data to be collected in IPT include measures of health and health-related behavior, nutritional status, activities of daily living, functional capacity, and cognition. The questionnaire phase covers self-perceived impairment due to health-related outcomes, personality, and measures of the environment including life events, social support, socioeconomic status and the family environment. The powerful adoption/twin design of SATSA provides a compelling basis for analyzing issues of genetic and environmental contributions to change and continuity in biobehavioral aging. Extension of SATSA to three measurement occasions will enable quantitative genetic analyses of research issues related to the shape of growth curves, such as the importance of genetic factors for terminal decline and reduction in functional capacity. Three points of measure provide a more appropriate basis for examining structural change in the relationship of measures within and between biobehavioral domains. Thus, analyses will also be concerned with assessing the extent to which genetic and environmental factors mediate the relationship between health, cognition and well-being in the elderly. More refined analyses of the etiology of developmental turning-points and the mechanisms contributing to longitudinal stability and change will be possible with the inclusion of a fourth occasion. Predictive relationships, such as the impact of life events and social support on cognitive and health outcomes at subsequent occasions, will also be the object of study.